Rankine cycle device of internal combustion engine

ABSTRACT

A Rankine cycle system includes a first Rankine cycle ( 2 A) operated by a first working medium and a second Rankine cycle ( 2 B) operated by a second working medium. The first Rankine cycle ( 2 A) is constituted from an evaporator ( 3 A), an expander ( 4 ), a condenser ( 5 A) and a supply pump ( 6 A), and the second Rankine cycle ( 2 B) is constituted from an evaporator ( 3 B), the expander ( 4 ), a condenser ( 5 B) and a supply pump ( 6   c ). The evaporator ( 3 A) in the first Rankine cycle ( 2 A) and the evaporator ( 3 B) in the second Rankine cycle ( 2 B) are disposed at locations upstream and downstream of an exhaust emission control device ( 8 ) mounted in an exhaust passage ( 7 ) for the internal combustion engine ( 1 ). The first working medium has a boiling point higher than that of the second working medium, and the capacity of the pump ( 6 A) in at least the first Rankine cycle ( 2 A) is variable. Thus, the efficiency of recovery of a waste heat from the internal combustion engine by the Rankine cycle system can be enhanced to the maximum, and the activation of the exhaust emission control device can be promoted.

FIELD OF THE INVENTION

[0001] The present invention relates to a Rankine cycle system for aninternal combustion engine, including a first Rankine cycle operated bya first working medium and a second Rankine cycle operated by a secondworking medium.

BACKGROUND ART

[0002] There are waste-heat recovery systems known from Japanese PatentApplication Laid-open Nos.60-93110 and 8-68318, each of which includesheat exchangers mounted at locations upstream and downstream of anexhaust emission control device mounted in an exhaust passage for aninternal combustion engine, so that water as a working medium issupplied to the heat exchangers where it is subjected to a heat exchangewith an exhaust gas. There are also Rankine cycle systems known fromJapanese Patent No.2650660, each of which including an evaporator, anexpander, a condenser and a supply pump, wherein a mixture of a mediumhaving a higher boiling point and a medium having a lower boiling pointis used as a working medium.

[0003] In an internal combustion engine including an exhaust emissioncontrol device mounted in an exhaust passage, a catalyst in the exhaustemission control device is not activated in a lower-temperature stateimmediately after the start of the internal combustion engine and hence,the exhaust emission control performance is temporarily degraded. Forthis reason, it is required that the catalyst is heated and activatedpromptly by heat of an exhaust gas. However, if an evaporator in aRankine cycle system is disposed at a location upstream of the exhaustemission control device, the following problem is encountered: theexhaust gas is robbed of its heat by the evaporator and hence, theactivation of the catalyst is retarded. If an evaporator is alsodisposed at a location downstream of the exhaust emission control devicein addition to the location upstream of the exhaust emission controldevice, then the exhaust gas is robbed of its heat immediately after thestart of the internal combustion engine by the upstream evaporator andthe exhaust emission control device. For this reason, the downstreamevaporator cannot generate a sufficient amount of vapor and thus, it isdifficult to effectively operate the Rankine cycle system.

DISCLOSURE OF THE INVENTION

[0004] The present invention has been accomplished with theabove-described circumstances in view, and it is an object of thepresent invention to ensure that the efficiency of recovery of a wasteheat from an internal combustion engine by a Rankine cycle system isincreased to the maximum, and the activation of a catalyst in an exhaustemission control device is promoted.

[0005] To achieve the above object, according to a first aspect andfeature of the present invention, there is proposed a Rankine cyclesystem for an internal combustion engine, comprising a first Rankinecycle operated by a first working medium and a second Rankine cycleoperated by a second working medium, each of the Rankine cycles beingcomprised of an evaporator for heating a liquid-phase working medium bywaste heat from the internal combustion engine to generate a vapor, anexpander for converting the heat energy of the vapor discharged by theevaporator into a mechanical energy, a condenser for cooling the vapordischarged by the expander to return the vapor into the liquid-phaseworking medium, and a supply pump for supplying the water discharged bythe condenser to the evaporator, wherein the evaporator in the firstRankine cycle and the evaporator in the second Rankine cycle aredisposed at locations upstream and downstream of an exhaust emissioncontrol device mounted in an exhaust passage for the internal combustionengine; the first working medium is of a boiling point higher than thatof the second working medium; and the capacity of the supply pump in atleast the first Rankine cycle is variable.

[0006] With the above arrangement, if the amount of first working mediumsupplied to the evaporator in the first Rankine cycle mounted at thelocation upstream of the exhaust emission control device is decreased,or such supplying of the first working medium is stopped immediatelyafter the start of the internal combustion engine or during a lower-loadoperation of the internal combustion engine, the heat energy of anexhaust gas can be applied effectively to the exhaust emission controldevice to activate a catalyst in the exhaust emission control device,thereby enhancing the exhaust gas purifying effect. Moreover, the secondworking medium flowing through the evaporator in the second Rankinecycle mounted at the location downstream of the exhaust emission controldevice is of the lower boiling point and hence, can be converted easilyinto the vapor by the lower-temperature exhaust gas immediately afterthe start of the internal combustion engine or during the lower-loadoperation of the internal combustion engine to operate the expanderwithout hindrance.

[0007] If the working media are supplied to the evaporator in the firstRankine cycle mounted at the location upstream of the exhaust emissioncontrol device and evaporator in the second Rankine cycle mounted at thelocation downstream of the exhaust emission control device,respectively, during a higher-load operation of the internal combustionengine after completion of the warming of the engine, the heat energy ofthe exhaust gas can be recovered to the maximum to increase the outputfrom the expander. Moreover, the first working medium flowing in theexpander on an upstream side where the temperature of the exhaust gas ishigher is of the higher boiling point, and the second working mediumflowing in the expander on a downstream side where the temperature ofthe exhaust gas is lower is of the lower boiling point and hence, theheat energy of the exhaust gas can be recovered further effectively.

[0008] According to a second aspect and feature of the presentinvention, in addition to the first feature, the expander includeshigher-pressure expanding portions and lower-pressure expandingportions, so that outputs from both of the expanding portions can beunited together and output from a common rotary shaft; the vapor of thefirst working medium is supplied to the higher-pressure expandingportions; and the vapor of the second working medium is supplied to thelower-pressure expanding portions.

[0009] With the above arrangement, the expander includes thehigher-pressure expanding portions to which the vapor of the firstworking medium is supplied, and the lower-pressure expanding portions towhich the vapor of the second working medium is supplied, so that theoutputs from both of the expanding portions are united together andoutput from the rotary shaft. Therefore, a special output-uniting meansis not required to be mounted, leading to a simplified structure.

[0010] Cylinders 33 and vane chambers 50 in an embodiment correspond tothe higher-pressure and lower-pressure expanding chambers of the presentinvention, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGS. 1 to 12 show an embodiment of the present invention.

[0012]FIG. 1 is a schematic diagram of a Rankine cycle system for aninternal combustion engine;

[0013]FIG. 2 is a vertical sectional view of an expander, correspondingto a sectional view taken along a line 2-2 in FIG. 4;

[0014]FIG. 3 is an enlarged sectional view of an area around arotational axis in FIG. 2;

[0015]FIG. 4 is a sectional view taken along a line 4-4 in FIG. 2;

[0016]FIG. 5 is a sectional view taken along a line 5-5 in FIG. 2;

[0017]FIG. 6 is an enlarged view of a portion of FIG. 4;

[0018]FIG. 7 is an enlarged sectional view taken along a line 7-7 inFIG. 3;

[0019]FIG. 8 is a diagram showing sectional shapes of a rotor chamberand a rotor;

[0020]FIG. 9 is an exploded perspective view of the rotor;

[0021]FIG. 10 is an exploded perspective view of a rotor segment;

[0022]FIG. 11 is an exploded perspective view of a vane; and

[0023]FIG. 12 is an exploded perspective view of a rotary valve.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] An embodiment of the present invention will now be described withreference to FIGS. 1 to 12.

[0025] Referring to FIG. 1, a Rankine cycle system using an exhaust gasfrom an internal combustion engine 1 as a heat source is comprised of afirst Rankine cycle 2A and a second Rankine cycle 2B using working mediaindependent from each other. An exhaust emission control device 8 of aternary catalyst type is mounted in an exhaust passage 7 for theinternal combustion engine 1; and a first evaporator 3A is mounted at alocation upstream of the exhaust emission control device 8, and a secondevaporator 3B is mounted at a location downstream of the exhaustemission control device 8.

[0026] The first Rankine cycle 2A includes the first evaporator 3A forgasifying a first working medium having a high boiling point (water inthe embodiment) by heat of the exhaust gas to generate vapor in ahigh-temperature and a high-pressure state, an expander 4 for generatingan output by th expansion of the vapor, a first condenser 5A forliquefying the vapor having a temperature and a pressure dropped byconverting a pressure energy into a mechanical energy in the expander 4,and a first supply pump 6A for supplying the water from the firstcondenser 5A in a pressurized state again to the first evaporator 3A.The evaporator 3A, the expander 4, the condenser 5A and the supply pump6A in the first Rankine cycle 2A are connected to one another bypassages A1 to A4 to constitute a closed loop.

[0027] The second Rankine cycle 2B includes the second evaporator 3B forgasifying a second working medium having a low boiling point (pentene orsubstitution flon in the embodiment) by heat of the exhaust gas togenerate vapor in a high-temperature and a high-pressure state, theexpander 4 for generating an output by the expansion of the vapor, asecond condenser 5B for liquefying the vapor having a temperature and apressure dropped by converting the pressure energy into the mechanicalenergy in the expander 4, and a second supply pump 6B for supplying thewater from the second condenser 5B in a pressurized state again to thesecond evaporator 3B. The evaporator 3B, the expander 4, the condenser5B and the supply pump 6B in the second Rankine cycle 2B are connectedto one another by passages B1 to B4 to constitute a closed loop.

[0028] The expander 4 is used commonly in the first Rankine cycle 2A andthe second Rankine cycle 2B, but the first working medium and the secondworking medium cannot be mixed together in the expander 4. Morespecifically, the first working medium in the first Rankine cycle 2Agenerates a shaft torque in each of cylinders 33 which are high-pressureexpanding portions of the expander 4, and the second working medium inthe second Rankine cycle 2B generates a shaft torque in each of vanechambers 50 which are low-pressure expanding portions of the expander 4.Both of the shaft torques are united with each other in the expander 4and output from a common rotary shaft 21.

[0029] The flow rate of the working medium in the first Rankine cycle2A, namely, the capacity of the first supply pump 6A is controlled by anelectronic control unit 10, based on a temperature of a catalyst in theexhaust emission control device 8 detected by a temperature sensor 9.

[0030] The entire structure of the expander 4 will be described belowwith reference to FIGS. 2 to 6.

[0031] The expander 4 has a casing 11, which is comprised of first andsecond casing halves 12 and 13 made of a metal. The first and secondcasing halves 12 and 13 comprise bodies 12 a, 13 a defining a rotorchamber 14 by cooperation with each other, and circular flanges 12 b, 13b integrally connected to outer peripheries of the bodies 12 a, 13 a,respectively. The circular flanges 12 b and 13 b are coupled to eachother through a metal gasket 15. An outer surface of the first casinghalf 12 is covered with an intake chamber outer-wall 16 having a deepbowl-shape, and a circular flange 16 a integrally connected to an outerperiphery of the outer wall 16 is superposed on a left side of thecircular flange 12 b of the first casing half 12. An outer surface ofthe second casing half 13 is covered with an exhaust chamber outer-wall17 in which a magnet coupling (not shown) for transmitting the outputfrom the expander 4 to the outside is accommodated, and a circularflange 17 a integrally connected to an outer periphery of the outer wall17 is superposed on a right side of the circular flange 13 b of thesecond casing half 13. The four circular flanges 12 a, 13 a, 16 a and 17a are fastened commonly by a plurality of bolts disposedcircumferentially. An intake chamber 19 is defined between the intakechamber outer-wall 16 and the first casing half 12, and an exhaustchamber 20 is defined between the exhaust chamber outer-wall 17 and thesecond casing half 13. A discharge bore 17 b for guiding thedropped-temperature and dropped-pressure vapor finishing its work in theexpander 4 to the second condenser 5B is provided in the exhaust chamberouter-wall 17.

[0032] Each of the bodies 12 a and 13 a of the casing halves 12 and 13has a hollow bearing tube 12 c, 13 c protruding outwards, and a rotaryshaft 21 having a hollow 21 a is rotatably supported in the hollowbearing tubes 12 c and 13 c with a pair of bearing members 22 and 23interposed therebetween. Thus, an axis L of the rotary shaft 21 extendsthrough an intersection between a longer diameter and a shorter diameterin a rotor chamber 14. A smaller-diameter portion 21 b at a right end ofthe rotary shaft 21 extends through the hollow bearing tube 13 c of thesecond casing half 13 into the exhaust chamber 20, and a rotor boss 24of the magnet coupling is spline-coupled to the smaller-diameter portion21 b. An outer periphery of the smaller-diameter portion 21 b at theright end of the rotary shaft 21 and an inner periphery of the hollowbearing tube 13 c of the second casing half 13 are sealed from eachother by a seal member 25, which is fixed by a nut 26 threadedly fittedto the inner periphery of the hollow bearing tube 13 c.

[0033] As can be seen from FIGS. 4 and 8, a circular rotor 27 isaccommodated in the rotor chamber 14 having a pseudo elliptic shape. Therotor 27 is fitted over and integrally coupled to an outer periphery ofthe rotary shaft 1 by a pin 28, and an axis of the rotor 27 and an axisof the rotor chamber 14 are brought in line with the axis L of therotary shaft 21. The rotor chamber 14 has a pseudo elliptic shape asviewed in a direction of the axis L and has a longer diameter DL and ashorter diameter DS. The rotor 27 has a truly circular shape as viewedin the direction of the axis L and has a diameter DR slightly smallerthan the shorter diameter DS of the rotor chamber 14.

[0034] Each of the rotor chamber 14 and the rotor 27 has a sectionalshape similar to a track for a field competition as viewed in adirection perpendicular to the axis L. More specifically, the sectionalshape of the rotor chamber 14 is formed from a pair of flat faces 14 a,14 a extending in parallel to and at a distance d left between eachother, and an arcuate face 14 b connecting outer peripheries of the flatfaces 14 a, 14 a smoothly to each other and having a center angle of180°. Likewise, the sectional view of the rotor 27 is formed from a pairof flat faces 27 a, 27 a extending in parallel to and at a distance dleft between each other, and an arcuate face 27 b connecting outerperipheries of the flat faces 27 a, 27 a smoothly to each other andhaving a center angle of 180°. Therefore, the flat faces 14 a, 14 a ofthe rotor chamber 14 and the flat faces 27 a, 27 a of the rotor 27 arein contact with each other and thus, a pair of crescent-shaped spaces(see FIG. 4) are defined between an inner peripheral surface of therotor chamber 14 and an outer peripheral surface of the rotor 27.

[0035] The structure of the rotor 27 will be described below in detailwith reference to FIGS. 3, 6, 9 and 10.

[0036] The rotor 27 is comprised of a rotor core 31 fixed to the outerperiphery of the rotary shaft 21, and twelve rotor segments 32 fixed tocover the periphery of the rotor core 31 and forming an outer shell ofthe rotor 27. The rotor core 31 includes a disk-shaped main body 31 a,and gear-shaped boss portions 31 b, 31 b protruding in axially oppositedirections from a center portion of the main body 31 a. Twelve cylinders33 made of a ceramic (or carbon) are mounted radially at distances of30° in the main body 31 a and fixed by caps 34 and keys 35, so that theyare prevented from being withdrawn. A smaller-diameter portion 33 a isprojecting provided at an inner end of each of the cylinders 33 andsealed at its base end from the main body 31 a of the rotor core 31 withan O-ring interposed therebetween. A tip end of the smaller-diameterportion 33 a is fitted over the outer peripheral surface of the hollowrotary shaft 21, and cylinder bores 33 b communicate with the hollow 21a in the rotary shaft 21 through twelve third vapor passages S3extending through the smaller-diameter portions 33 a and the rotaryshaft 21. A piston 37 made of a ceramic is slidably received in each ofthe cylinders 33. When the piston 37 is moved to a radially innermostposition, it is retracted and sunk completely in the cylinder bore 33 b,and when the piston 37 is moved to radially outermost position, abouthalf of the entire length of the piston 37 protrudes to the outside ofthe cylinder bore 33 b.

[0037] Each of the rotor segments 32 is comprised of five componentscoupled to one another. The five components are a pair of block members38, 38 having hollows 38 a, 38 a, a pair of side plates 39, 39 each madeof a U-shaped plate material, and a bottom plate 40 made of arectangular plate material, all of which are integrally coupled to oneanother by brazing.

[0038] Two recesses 38 b and 38 c are defined in an outer peripheralsurface of each of the block members 38, namely, in a surface opposed toeach of the flat faces 14 a, 14 a of the rotor chamber 14 to extend inan arcuate shape about the axis L, and lubricating-water ejection bores38 d and 38 e open into central portions of the recesses 38 b and 38 c.A twenty first water passage W20 and a twenty second water passage W21are defined in a recessed manner in a surface of the block member 38coupled to the side plate 39.

[0039] An orifice-defined member 41 having twelve orifices is fittedinto a central portion of the bottom plate 40, and an O-ring 42 mountedto the bottom plate 40 to surround the orifice-defined member 41 sealsthe orifice-defined member 41 and the outer peripheral surface of themain body 31 a of the rotor core 31 from each other. Fourteenth tonineteenth water passages W14 to W19 are provided two by two in arecessed manner in a surface of the bottom plate 40 coupled to the blockmember 38 to extend radially from the orifice-defined member 41. Thefourteenth to nineteenth water passages W14 to W19 extend toward thesurface coupled to the side plate 39.

[0040] Twenty second to twenty seventh water passages W22 to W27 areprovided in a recessed manner in a surface of each side plate 39 coupledto the block members 38, 38 and the bottom plate 40. The fourteenthwater passage W14, the fifteenth water passage W15, the eighteenth waterpassage W18 and the nineteenth water passage W19 in an outer area of thebottom plate 40 communicate with the twenty second water passage W22,the twenty third water passage 23, the twenty sixth water passage W26and the twenty seventh water passage W27 in the side plate 39, and thesixteenth water passage W16 and the seventeenth water passage W27 in aninner area of the bottom plate 40 communicate with the twenty fourthwater passage W24 and the twenty fifth water passage W25 in the sideplate 39 through the twentieth water passage W20 and the twenty firstwater passage W21 in the block member 38. Outer ends of the twentysecond water passage W22, the tw nty fifth water passage W25, the twentysixth water passage W26 and the twenty seventh water passage W27 in theside plate 39 open as four lubricating water ejection bores 39 a intothe outer surface of the side plate 39. Outer ends of the twenty thirdwater passage W23 and the twenty fourth water passage W24 in the sideplate 39 communicate with the lubricating oil ejection bores 38 d and 38e in the recesses 38 b and 38 c through a twenty eighth water passageW28 and a twenty ninth water passage W29 defined in each of the blockmembers 38, 38, respectively. A notch 39 b having a partially arcuatesection is formed in the outer surface of the side plate 39 in order toavoid the interference with the piston 37 moved radially outwards. Thereason why the twentieth water passage W20 and the twenty first waterpassage W21 are defined in the block member 38 rather than in the sideplate 39 is that the side plate 39 has a thickness decreased byprovision of the notch 39 b, and a thickness enough to define thetwentieth water passage W20 and the twenty first water passage W21 canbe ensured in the block member 38.

[0041] As shown in FIGS. 2, 5, 9 and 11, twelve vane grooves 43 aredefined between the adjacent rotor segments 32 of the rotor 27 to extendradially, and plate-shaped vanes 44 are slidably received in the vanegrooves 43, respectively. Each of the vanes 44 is formed into asubstantially U-shape and includes parallel faces 44 a, 44 a extendingalong the parallel faces 14 a, 14 a of the rotor chamber 14, an arcuateface 44 b extending along the arcuate face 14 b of the rotor chamber 14,and a notch 44 c located between the parallel faces 44 a, 44 a. Rollers45, 45 having a roller bearing structure are rotatably supported on apair of support shafts 44 d, 44 d protruding from the parallel faces 44a, 44 a, respectively.

[0042] A seal member 46 made of a synthetic resin and formed into aU-shape is retained on the arcuate face 44 b of the vane 44, and has atip end protruding slightly from the arcuate face 44 b of the vane 44 tocome into sliding contact with the arcuate face 14 b of the rotorchamber 14. Sliding members 47, 47 made of a synthetic resin are fixedto the parallel faces 44 a, 44 a of the vane 44 to come into slidingcontact with the parallel faces 14 a, 14 a of the rotor chamber 14.Sliding members 48, 48 of a synthetic resin are also fixed to oppositesides of the notch 44 c of the vane 44 to come into sliding contact withthe main body 31 a of the rotor core 31. Two recesses 44 e, 44 e aredefined in each of opposite sides of the vane 44 and opposed to radiallyinner two of the four lubricating water ejection bores 39 a opening intothe outer surfaces of the side plates 39, 39 of the rotor segment 32. Aprojection 44 f provided at a central portion of the notch 44 c of thevane 44 in a protruding manner to face radially inwards abuts against aradially outer end of the piston 37. A water discharge passage 44 g isdefined in the vane to extend radially, and opens at its radially innerend into a tip end of the projection 44 f and at its radially outer endinto one of sides of the vane 44. A location at which the waterdischarge passage 44 g opens into the one side of the vane 44 faces to apoint radially outer than the arcuate face 27 b of the rotor 27, whenthe vane 44 is moved to protrude to the radially outermost position.

[0043] Annular grooves 49, 49 having a pseudo elliptic shape similar toa rhombic shape with four apexes rounded are provided in a recessedmanner in the flat faces 14 a, 14 a of the rotor chamber 14 defined bythe first and second casing halves 12 and 13, and the pair of rollers45, 45 of each of the vanes 44 are rollably engaged in the annulargrooves 49, 49. The distance between each of the annular grooves 49, 49and the arcuate face 14 b of the rotor chamber 14 is constant over theentire periphery. Therefore, when the rotor 44 is rotated, the vane 44with the rollers 45, 45 guided in the annular grooves 49, 49 isreciprocally moved radially within the vane groove 43 and slid along thearcuate face 14 b of the rotor chamber 14 in a state in which the sealmember 46 mounted to the arcuate face 44 b of the vane 44 has beencompressed at a given amount. Thus, it is possible to reliably seal thevane chambers 50 defined between the adjacent vanes 44, while preventingthe rotor chamber 14 and the vanes 44 from being brought into directsolid contact with each other to prevent an increase in slidingresistance and the occurrence of the wearing.

[0044] A pair of circular seal grooves 51, 51 are defined in the flatfaces 14 a, 14 a of the rotor chamber 14 to surround the outer sides ofthe annular grooves 49, 49. A pair of ring seals 52 each having twoO-rings 52 and 53 are slidably received in the circular seal grooves 51,respectively, and have sealing faces opposed to the recesses 38 b and 38c defined in each of the rotor segments 32. The pair of ring seals 54,54 are prevented from being turned relative to the first and secondcasing halves 12 and 13 by knock pins 55, 55, respectively.

[0045] The assembling of the rotor 27 is carried out in the followingmanner: In FIG. 9, the twelve rotor segments 32 are fitted over theouter periphery of the rotor core 31 having the cylinders 33, the caps34 and the keys 35 previously assembled thereto, and the vanes 44 arefitted into the twelve vane grooves 43 defined between the adjacentrotor segments 32. At this time, a shim having a predetermined thicknessis disposed on each of opposite sides of each vane 44 in order to definea clearance between each of the vanes 44 and each of the side plates 39of the rotor segments 32. In this state, the rotor segments 32 and thevanes 44 are tightened radially inwards to the rotor core 31 using ajig, and the rotor segments 32 are positioned accurately relative to therotor core 31. Thereafter, the rotor segments 32 are temporarily fixedto the rotor core 31 by temporarily fixing bolts 58 (see FIG. 2). Then,the rotor 27 is removed from the jig, and the pinholes 56, 56 are madein each of the rotor segments 32 to extend through the rotor core 31.The knock pins 57, 57 are press-fitted into the pinholes 56, 56, wherebyrotor segments 32 are coupled to the rotor core 31.

[0046] As can be seen from FIGS. 3, 7 and 12, the pair of bearingmembers 22 and 23 supporting the outer peripheral surface of the rotaryshaft 21 has an inner peripheral surface which is tapered, so that itsdiameter is increased toward the rotor 27. The axially outer ends of thebearing members 22 and 23 are engaged in the hollow bearing tubes 12 cand 13 c of the first and second casing halves 12 and 13, so that theyare prevented from being turned. It should be noted that the outerperiphery at the left and of the rotary shaft 21 supported in the lefthollow bearing tube 12 c is constituted by a different member 21 c inorder to enable the assembling of the rotor 27 to the rotary shaft 21.

[0047] An opening 16 b is defined in the center of the relay chamberouter-wall 16, and a boss portion 61 a of a valve housing 61 disposed onthe axis L is fixed to an inner surface of the opening 16 b by aplurality of bolts 62 and also fixed to the first casing half 12 by anut 63. A cylindrical first fixing shaft 64 is relatively rotatablyfitted in the hollow 21 a in the rotary shaft 21, and a second fixingshaft 65 is coaxially fitted to an inner periphery of a right end of thefirst fixing shaft 64. An outer peripheral portion of a right end of thesecond fixing shaft 65 protruding from the first fixing shaft 64 and thehollow 21 a in the rotary shaft 21 are sealed from each other by anO-ring 66. The valve housing 61 extending within the first fixing shaft64 includes a flange 61 b, and an O-ring 67, a thickened portion 64 a ofthe first fixing shaft 64, an O-ring 68, a washer 69, a nut 70 and thesecond fixing shaft 65 are fitted sequentially at the right of theflange 61 b. The nut 70 and the second fixing shaft 65 are threadedlycoupled to the valve housing 61 and hence, the thickened portion 64 a ofthe first fixing shaft 64 is positioned between the flange 61 b of thevalve housing 61 and the washer 69 with the pair of O-rings 66 and 67interposed therebetween.

[0048] The first fixing shaft 64 supported on the inner periphery of thehollow bearing tube 12 c of the first casing half 12 with an O-ring 71interposed therebetween is connected at its left end to the boss portion61 a of the valve housing 61 by a ring-shaped Oldham coupling 72, andthe deflection of the rotor 27 supported on the outer periphery of thefirst fixing shaft 64 through the rotary shaft 21 can be permitted bypermitting the radial deflection of the first fixing shaft 64 by theOldham coupling 72. In addition, the first fixing shaft 64 is preventedfrom being turned relative to the casing 11 by fixing arms 73 a, 73 a ofa detent member 73 loosely fitted in the left end of the first fixingshaft 64 to the first casing half 12 by bolts 74, 74.

[0049] A vapor supply pipe 75 is fitted within the valve housing 61disposed on the axis L and is fixed to the valve housing 61 by a nut 76.The vapor supply pipe 75 is connected at its right end to a nozzlemember 77 press-fitted into the valve housing 61. A pair of recesses 81,81 (see FIG. 7) are defined at a phase difference of 180° astride thevalve housing 61 and a tip end of the nozzle member 77, and annularjoint members 78, 78 are fitted into and retained in the recesses 81,81. A first vapor passage S1 is defined axially in the center of thenozzle member 77 to lead to the vapor supply pipe 75, and a pair ofsecond vapor passages S2, S2 are provided at a phase difference of 180°to extend axially through the thickened portion 64 a of the first fixingshaft 64. A terminal end of the first vapor passage S1 and radiallyinner ends of the second vapor passages S2, S2 are always incommunication with each other through the joint members 78, 78. Twelvethird vapor passages S3 are provided to extend through the rotary shaft21 and the smaller-diameter portions 33 a of the twelve cylinders 33retained at the distances of 30° in the rotor 27 fixed to the rotaryshaft 21, as described above. Radially inner ends of the third vaporpassages S3 are opposed to radially outer ends of the second vaporpassage S2, S2 to be able to communicate with them.

[0050] A pair of notches 64 b, 64 b are defined at a phase difference of180° in the outer peripheral surface of the thickened portion 64 a ofthe first fixing shaft 64, and are capable of communicating with thethird vapor passages S3. The notches 64 b, 64 b communicate with a vapordischarge pipe 61 c extending through the intake chamber outer-wall 17through a pair of fourth vapor passages S4, S4 defined obliquely in thefirst fixing shaft 64, a fifth vapor passage S5 defined axially in thefirst fixing shaft 64 and a sixth vapor passage S6 defined in the bossportion 61 a of the valve housing 61.

[0051] As shown in FIG. 5, a plurality of intake ports 79 are defined ina radial arrangement in the first casing half 12 at locations advancedat an angle of 15° in a direction of rotation of the rotor 27, based ona direction of the shorter-diameter of the rotor chamber 14. Theinternal space in the rotor chamber 14 communicates with the intakechamber 19 by virtue of the intake ports 79. A large number of exhaustports 80 are provided and arranged in a plurality of radial arrays inthe second casing half 13 at locations delayed at an angle of 15° to 75°in the direction of rotation of the rotor 27, based on the direction ofthe shorter-diameter of the rotor chamber 14. The internal space in therotor chamber 14 communicates with the exhaust chamber 20 by virtue ofthe exhaust ports 80.

[0052] A rotary valve V is formed to permit the periodical communicationof the second vapor passages S2, S2 and the third vapor passages S3 witheach other as well as the periodical communication of the notches 64 b,64 b in the first fixing shaft 64 and the third vapor passages S3 witheach other by relative rotation of the first fixing shaft 64 and therotary shaft 21.

[0053] As can be seen from FIGS. 2 and 3, pressure chambers 86, 86 aredefined in backs of the ring seals 54, 54 fitted in the circular sealgrooves 51, 51 in the first and second casing halves 12 and 13, and afirst water passage W1 defined in the first and second casing halves 12and 13 communicates with both of the pressure chambers 86, 86 through asecond water passage W2 and a third water passage W each comprising apipe. A filter chamber 13 d capable of being opened and closed by acover 89 provided with two O-rings 87 and 88 is defined radially outsidethe hollow bearing tube 13 c of the second casing half 13, and anannular filter 90 is accommodated in the filter chamber 13 d. The firstwater passage W1 in the second casing half 13 communicates with an outerperipheral surface of the filter 90 through a fourth water passage W4comprising a pipe, and an inner peripheral surface of the filter 90communicates with a sixth annular water passage W6 defined between thesecond casing half 13 and the rotary shaft 21 through a fifth waterpassage W5 defined in the second casing half 13. The sixth water passageW6 communicates with the twelve orifice-defined members 41 throughtwelve seventh water passages W7 extending axially within the rotaryshaft 21, an annular groove 21 d defined in the outer periphery of therotary shaft 21 and twelve eighth water passages W8 extending radiallywithin the rotor core 31, respectively.

[0054] The annular groove 21 d defined in the outer periphery of therotary shaft 21 communicates with an annular groove 21 e defined in theouter periphery of the rotary shaft 21 through twelve ninth waterpassages W9 (see FIG. 7) extending axially, and the annular groove 21 ecommunicates with an eleventh annular water passage W11 defined betweenthe left end of the rotary shaft 21 and the first housing half 12through twelve tenth water passages W10 extending axially within therotary shaft 21. The sixth annular water passage W6 and the eleventhannular water passage W11 communicate with sliding surfaces between theinner peripheries of the bearing members 22 and 23 and the outerperiphery of the rotary shaft 21 through orifices around outerperipheries of orifice-defining bolts 91 threadedly fitted in thebearing members 22 and 23 and further via twelfth water passages W12defined in the bearing members 22 and 23. The sliding surfaces betweenthe inner peripheries of the bearing members 22 and 23 and the outerperiphery of the rotary shaft 21 communicate with the vane grooves 43via thirteenth draining water passages W13.

[0055] The sixth annular water passage W6 communicates with slidingportions between the inner peripheral surface of the hollow 21 a in therotary shaft 21 and the outer peripheral surface of the right end of thefirst fixing shaft 64 via two thirtieth water passages W30, W30 providedaxially in the rotary shaft 21. A seal groove 64 c defined at the rightof the thickened portion 64 a of the first fixing shaft 64 communicateswith the fifth vapor passage S5 through thirty first water passages W31,W31 provided obliquely in the first fixing shaft 64. The eleventhannular water passage W11 communicates with sliding portions between theinner peripheral surface of the hollow 21 a in the rotary shaft 21 andthe outer peripheral surface of the left end of the first fixing shaft64, and a seal groove 64 d defined at the left of the thickened portion64 a of the first fixing shaft 64 communicates with the fifth vaporpassage S5 through thirty second water passages S32, W32 extendingradially through the first fixing shaft 64 and the thirty first waterpassages W31, W31.

[0056] As can be seen from the comparison of FIGS. 1 and 2 with eachother, the high-temperature and high-pressure vapor from the firstevaporator 3A is supplied via a passage A1 to the vapor supply pipe 75for the expander 4, and the dropped-temperature and dropped-pressurevapor is discharged from the vapor discharge pipe 61 c of the expander 4via a passage A2 into the first condenser 5A. The high-temperature andhigh-pressure vapor from the second evaporator 3B is supplied via apassage B1 into the intake chamber 19 in the expander 4, and thedropped-temperature and dropped-pressure vapor is discharged from thedischarge bore 17B of the exhaust chamber 20 via a passage B2 into thesecond condenser 5B.

[0057] The operation of the present embodiment having theabove-described arrangement will be described below.

[0058] First, the operation of the expander 4 will be described.Referring to FIG. 3, the high-temperature and high-pressure vapor fromthe passage A1 leading to a downstream side of the first evaporator 3Ais supplied to the vapor supply pipe 75, the first vapor passage S1defined axially in the nozzle member 77 and the pair of second vaporpassages S2, S2 extending radially through the nozzle member 77, thejoint members 78, 78 and the thickened portion 64 a of the first fixingshaft 64. Referring to FIGS. 6 and 7, when the rotary shaft 21 rotatedin unison with the rotor 27 reaches a predetermined phase, the pair ofthird vapor passages S3, S3 existing at the locations advanced in thedirection of rotation of the rotor 27 shown by an arrow R from a shorterdiameter position of the rotor chamber 14 are put into communicationwith the pair of second vapor passages S2, S2, whereby thehigh-temperature and high-pressure vapor in the second vapor passagesS2, S2 is supplied into the pair of cylinders 33, 33 via the third vaporpassages S3, S3 to urge the pistons 37, 37 radially outwards. When thevanes 44, 44 urged by the pistons 37, 37 are moved radially outwards,the advancing movements of the pistons 37, 37 are converted into therotational movement of the rotor 27 by the engagement of the pair ofrollers 45, 45 mounted on the vanes 44, 44 and the annular grooves 49,49 with each other.

[0059] Even after the communication between the second vapor passagesS2, S2 and the third vapor passages S3, S3 is blocked with the rotationof the rotor 27 in the direction indicated by the arrow R, the pistons37, 37 are further advanced by the further continuation of the expansionof the high-temperature and high-pressure vapor within the cylinders 33,33, whereby the rotation of the rotor 27 is continued. When the vanes44, 44 reach a longer-diameter position of the rotor chamber 14, thethird vapor passages S3, S3 leading to the corresponding cylinders 33,33 are put into communication with the notches 64 b, 64 b of the firstfixing shaft 64, and the pistons 37, 37 urged by the vanes 44, 44 withthe rollers 45, 45 guided in the annular grooves 49, 49 are movedradially inwards, whereby the vapor in the cylinders 33, 33 is suppliedas a dropped-temperature and dropper-pressure vapor into the passage A2through the third vapor passages S3, S3, the notches 64 b, 64 b, thefourth vapor passages S4, S4, the fifth vapor passage S5, the sixthvapor passage S6 and the vapor discharge pipes 61 c.

[0060] The high-temperature and high-pressure vapor from the passage B1leading to a downstream side of the second evaporator 3B is supplied viathe intake chamber 19 and the intake ports 79 in the first casing half12 into the vane chamber 50 in the rotor chamber 14, namely, the spacedefined by the rotor chamber 14, the rotor 27 and the pair of adjacentvanes 44, 44, where the vapor is expanded to rotate the rotor 27. Thedropped-temperature and dropped-pressure vapor which has finished itswork is discharged from the exhaust ports 80 in the second casing half13 into the exhaust chamber 20 and supplied therefrom via the dischargebore 17 and the passage B2 into the second condenser 5B.

[0061] In this manner, the twelve pistons 37 are operated sequentiallyby the expansion of the high-temperature and high-pressure vapor fromthe first evaporator 3A to rotate the rotor 27 through the rollers 45,45 and the annular grooves 49, 49, and an output is produced from therotary shaft 21 by rotating the rotor 27 through the vanes 44 by thehigh-temperature and high-pressure vapor from the second evaporator 3B.

[0062] The lubrication of various sliding portions of the expansion 4 bythe water will be described below.

[0063] The supplying of the lubricating water is carried out utilizingthe first supply pump 6A (see FIG. 1) for supplying the water from thefirst condenser 5A under a pressure to the first evaporator 3A, and aportion of the water discharged by the first supply pump 6A is suppliedas a lubricating water to the first water passage W1 in the casing 11.By utilizing the first supply pump 6A to supply the water to staticpressure bearings at various portions of the expander 4, a special pumpis not required, leading to a reduction in number of parts.

[0064] The water supplied to the first water passage W1 is supplied viathe second water passage W2 and the third water passage W3 eachcomprising the pipe into the pressure chambers 86, 86 in the bottoms ofthe circular seal grooves 51, 51 in the first casing half 12 and thesecond casing half 13 to bias the ring seals 54, 54 toward the side ofthe rotor 27. The water supplied from the first water passage W1 to thefourth water passage W4 comprising the pipe, after being filtered by thefilter 90 to remove a foreign matter, is supplied to the fifth waterpassage W5 defined in the second casing half 13, the sixth water passageW6 defined between the second casing half 13 and the rotary shaft 21,the seventh water passages W7 defined within the rotary shaft 21, theannular groove 21 d in the rotary shaft 21 and the eighth water passagesW8 defined in the rotor core 31, where the water is further pressurizedby the centrifugal force produced with the rotation of the rotor 27 andthen supplied to the orifice-defined members 41 of the rotor segments32.

[0065] In each of the rotor segments 32, the water flowing through theorifice-defined member 41 into the fourteenth water passage 14 in thebottom plate 40 is passed through the twenty second water passage W22 inthe side plate 39 and ejected from the lubricating water ejection bores39 a, and the water flowing through the orifice-defined member 41 intothe seventeenth water passage W17 in the bottom plate 40 is passedthrough the twenty first water passage W21 in the block member 38 andthe twenty fifth water passage W25 in the side plate 39 and ejected fromthe lubricating water ejection bores 39 a. The water flowing through theorifice-defined member 41 into the eighteenth water passage W18 in thebottom plate 40 is passed through the twenty sixth water passage W26 inthe side plate 39 and ejected from the lubricating water ejection bores39 a, and the water flowing through the orifice-defined member 41 intothe nineteenth water passage W19 in the bottom plate 40 is passedthrough the twenty seventh water passage W27 in-the side plate 39 andejected from the lubricating water ejection bores 39 a. Lower two of thefour lubricating water ejection bores 39 a opening into the surface ofthe side plate 39 communicate with the insides of the recesses 44 e, 44e in the two vanes 44.

[0066] The water flowing through the orifice-defined member 41 into thefifteenth water passage W15 in the bottom plate 40 is passed through thetwenty third water passage W23 in the side plate 39 and the twenty ninthwater passage W29 in the block member 38 and ejected from thelubricating water ejection bore 38 e within the recess 38 c, and thewater flowing through the orifice-defined member 41 into the sixteenthwater passage W16 in the bottom plate 40 is passed through the twentiethwater passage W20 in the block member 38, the twenty fourth waterpassage W24 in the side plate 39 and the twenty eighth water passage W28in the block member 38 and ejected from the lubricating water ejectionbore 38 d within the recess 38 b.

[0067] The water ejected from the lubricating water ejection bores 39 ain the side plate 39 of each of the rotor segments 32 into the vanegroove 43 forms a static pressure bearing between the vane groove 43 andthe vane 44 slidably fitted in the vane groove 43 to support the vane 44in a floated state, thereby preventing the solid contact of the sideplate 39 of the rotor segment 32 and the vane 44 with each other toprevent the occurrences of the seizure and the wearing. By supplying thewater for lubricating the sliding surface of the vane 33 through theeighth water passage W8 provided radially in the rotor 27 in the abovemanner, the water can be pressurized by the centrifugal force, but alsothe temperature around the rotor 27 can be stabilized to reduce theinfluence due to the thermal expansion, and the set clearance can bemaintained to suppress the leakage of the vapor to the minimum.

[0068] A circumferential load applied to each of the vanes 44 (a load ina direction perpendicular to the plate-shaped vane 44) is a resultantforce derived from a load due to a difference between vapor pressuresapplied to the front and rear surfaces of the vane within the rotorchamber 14 and circumferential components of reaction forces receivedfrom the annular grooves 49, 49 by the rollers 45, 45 mounted on thevane 44, but these loads are varied periodically depending on the phaseof the rotor 27. Therefore, the vane 44 receiving such unbalanced loadperiodically shows such a behavior that it is inclined within the vanegroove 43.

[0069] If the vane 44 is inclined by the unbalanced load in this manner,the clearance between the vane 44 and the four lubricating waterdischarge bores 39 a opening into the side plates 39, 39 of the rotorsegments 32 on opposite sides of the vane 44 is varied and hence, thewater film in the widened portion of the clearance is carried away, andit is difficult for the water to be supplied into the narrowed portionof the clearance. For this reason, there is a possibility that thepressure is not built up at the sliding portions, whereby the vane 44 isbrought into direct contact with the sliding surfaces of the side plates39, 39 to become worn. According to the present embodiment, however, thewater is supplied through the orifices into the lubricating waterdischarge bores 39 a by the orifice-defined member 41 mounted on therotor segment 32 and hence, the above-described disadvantage isovercome.

[0070] More specifically, when the clearance between the lubricatingwater discharge bores 39 a and the vane 44 is widened, the pressure ofwater supplied is constant and hence, the flow rate of the water isincreased by an increase in amount of water flowing out of the clearancerelative to a constant pressure difference produced across the orificein a steady state, whereby the pressure difference across the orifice isincreased by virtue of an orifice effect, leading to a reduction in thepressure in the clearance, and as a result, a force for narrowing thewidened clearance back to the original width is generated. When theclearance between the lubricating water discharge bores 39 a and thevane 44 is narrowed, the amount of water flowing out of the clearance isreduced, leading to a reduction in pressure difference across theorifice, and as a result, a force for widening the clearance narroweddue to the in crease in pressure in the clearance back to the originalwidth is generated.

[0071] Even if the clearance between the lubricating water dischargebores 39 a and the vane 44 is varied by the load applied to the vane 44,as described above, the orifices automatically regulate the pressure ofthe water supplied to the clearance depending on the variation in sizeof the clearance and hence, the clearance between the vane 44 and eachof the side plates 39, 39 of the rotor segments 32 on the opposite sidesof the vane 44 can be maintained at a desired size. Thus, the water filmcan be always retained between the vane 44 and each of the side plates39, 39 to support the vane in the floated state, thereby reliablyavoiding that the vane 44 is brought into solid contact with the slidingsurface of each of the side plates 39, 39 to become worn.

[0072] In addition, the water is retained in each of the two recesses 44e, 44 e defined in each of the opposite surfaces of the vane 44 andhence, each of the recesses 44 e, 44 e serves as a pressure dam tosuppress a drop in pressure due to the leakage of the water. As aresult, the vane 44 clamped between the sliding surfaces of the pair ofside plates 39, 39 is brought into the floated state by means of thewater, whereby the sliding resistance can be decreased to near zero.When the vane 44 is moved reciprocally, the radial position of the vane44 relative to the rotor 27 is changed, but the vane 44 movedreciprocally can be always retained in the floated state to effectivelyreduce the sliding resistance, because the recesses 44 e, 44 e areprovided in the vane 44 rather than in the side plates 39, 39 andprovided in the vicinity of the rollers 45, 45 with the load appliedmost largely to the vane 44.

[0073] The water which has lubricated the sliding surfaces of the vaneon the side plates 39, 39 is moved radially outwards by the centrifugalforce to lubricate the sliding portions of the seal member 46 mounted onthe arcuate face 44 b of the vane 44 and the arcuate face 14 b of therotor chamber 14. The water which has finished the lubrication isdischarged from the rotor chamber 14 through the exhaust ports 80.

[0074] As described above, the water is supplied to the pressurechambers 86, 86 in the bottoms of the circular seal grooves 51, 51 inthe first casing half 12 and the second casing half 13 to bias the ringseals 54, 54 toward the side of the rotor 27, and the water is ejectedfrom the lubricating water ejection bores 38 d and 38 e defined withinthe recesses 38 b and 38 c in each of the rotor segments 32 to form thestatic pressure bearing on the sliding surface on the flat faces 14 a,14 a of the rotor chamber 14, whereby the flat faces 27 a, 27 a of therotor 27 can be sealed by the ring seals 54, 54 which are in the floatedstate within the circular seal grooves 51, 51. As a result, the vapor inthe rotor chamber 14 can be prevented from being leaked through theclearance between the rotor chamber 14 and the rotor 27. At this time,the ring seals 54, 54 and the rotor 27 are isolated from each other bythe water films supplied from the lubricating water ejection bores 38 dand 38 e, so that they cannot be brought into solid contact with eachother. In addition, even if the rotor 27 is inclined, the ring seals 54,54 within the circular seal grooves 51, 51 are inclined, following theinclination of the rotor 27, whereby the stable sealing performance canbe ensured, while suppressing the frictional force to the minimum.

[0075] The water which has lubricated the sliding portions of the ringseals 54, 54 and the rotor 27 is supplied to the rotor chamber 14 by thecentrifugal force and discharged therefrom via the exhaust ports 80 tothe outside of the casing 11.

[0076] On the other hand, the water supplied from the sixth waterpassage W6 flows via the orifices defined around the outer peripheriesof the orifice-defining bolts 91 in the bearing member 23 and thetwelfth water passages 12 to form the water film on sliding surfaces ofthe inner periphery of the bearing member 23 and the outer periphery ofthe rotary shaft 21 to support the outer periphery of a right half ofthe rotary shaft 21 in the floated state by the water film, therebylubricating the sliding surfaces in such a manner that the solid contactof the rotary shaft 21 and the bearing member 23 with each other isprevented to prevent the occurrences of the seizure and the wearing. Thewater supplied from the sixth water passage W6 to the seventh waterpassages W7, the ninth water passages W9, the tenth water passages W10and the eleventh water passage W11 defined in the rotary shaft 21 flowsvia the orifices defined around the outer peripheries of theorifice-defining bolts 91 in the bearing member 22 and the twelfth waterpassages W12 to form the water film on sliding surfaces of the innerperiphery of the bearing member 22 and the outer periphery of the rotaryshaft 21 to support the outer periphery of a left half of the rotaryshaft 21 in the floated state by the water film, thereby lubricating thesliding surfaces in such a manner that the solid contact of the rotaryshaft 21 and the bearing member 23 with each other is prevented toprevent the occurrences of the seizure and the wearing. The water whichhas lubricated the sliding surfaces of the bearing members 22 and 23 isdischarged via the thirteenth water passages W13 defined within thebearing members 22 and 23 into the vane grooves 43.

[0077] The water accumulated in the vane grooves 43 flows into the waterdischarge passages 44 g connecting the bottoms of the vanes 44 withone-sides of the vanes 44, but because the water discharge passages 44 gopen into the rotor chamber 14 in a predetermined angle range where thevanes 44 protrude most largely from the rotor 27, the water in the vanegrooves 43 is discharged via the water discharge passages 44 g into therotor chamber 14 under the action of a difference in pressure betweenthe vane grooves 43 and the rotor chamber 14.

[0078] The water supplied from the sixth water passage W6 via thethirtieth water passage W30 defined in the rotary shaft 21 lubricatesthe outer periphery of the first fixing shaft 64 and the right half ofthe sliding surface on the inner periphery of the rotary shaft 21, andis then discharged from the seal groove 64 c in the first fixing shaft64 via the thirty first water passages W31, W31 to the fifth vaporpassage S5. Further, the water from the eleventh water passage W11lubricates the outer periphery of the first fixing shaft 64 and the lefthalf of the sliding surface on the inner periphery of the rotary shaft21, and is then discharged from the seal groove 64 d in the first fixingshaft 64 via the thirty first water passage W31 to the fifth vaporpassage S5.

[0079] As described above, the rotor 27 of the expander 4 is constitutedin a divided manner by the rotor core 31 and the plurality of rotorsegments 32 and hence, the dimensional accuracy of the vane grooves 43in the rotor 27 can be enhanced easily. In the simple rotor 27, it isextremely difficult to make the vane grooves 43 with a groove widthhaving a good accuracy to enhance the surface roughness of the slidingsurface, but such problem can be solved by assembling the plurality ofpreviously fabricated rotor segments to the rotor core 31. Moreover,even if an error is accumulated due to the assembling of the pluralityof rotor segments 32, the accumulation of error can be absorbed byregulating the size of last one of the rotor segments 32, therebyfabricating the rotor 27 having a high accuracy as a whole.

[0080] The inner rotor core 31 to which the high-temperature andhigh-pressure vapor is supplied and each of the outer rotor segments 32relatively low in temperature are formed by the different members.Therefore, the transmission of heat from the rotor core 31 having thehigh temperature to the rotor segments 32 can be suppressed, whereby thedissipation of heat to the outside of the rotor 27 can be prevented toenhance the thermal efficiency, but also the thermal deformation of therotor 27 can be moderated to enhance the accuracy. Moreover, a materialand a processing method suitable for each of the functions of the rotorcore 31 and the rotor segments 32 can be selected and hence, the degreeof freedom of the design and the degree of freedom of the processingmethod are increased, and the alleviation of the wearing of the slidingsurfaces of the rotor segments 32 and the vanes 44, an enhancement indurability and an enhancement in sealability can be achieved. Further,even when a disadvantage is arisen in a portion of the rotor 27, therotor 27 can be repaired only by replacing such portion by a newportion. This can contribute to a reduction in cost, as compared with acase where the entire rotor is replaced by a new rotor, or is discarded.

[0081] When the warming operation of the internal combustion engine 1 isstill uncompleted, or during the low-load operation of the internalcombustion engine 1, the catalyst in the exhaust emission control device8 is brought into an inactive state without sufficient rise in itstemperature and hence, it is necessary to heat the catalyst quickly byheat of an exhaust gas to activate it. In this state, the temperature ofthe catalyst detected by the temperature sensor 9 mounted on the exhaustemission control device 8 is equal to or lower than a presettemperature. For this reason, the first supply pump 6A in the firstRankine cycle 2A is stopped or reduced in capacity by a command from theelectronic control unit 10 and thus, the water is not circulated throughthe inside of the first evaporator 3A, or the amount of water circulatedthrough the inside of the first evaporator 3A is reduced. As a result,the heat of the exhaust gas from the internal combustion engine 1 can besupplied to the exhaust emission control device 8 without being littlerobbed of its heat during passing through the first evaporator 3A,thereby heating the catalyst quickly to activate it. Moreover, thepentene or the substitute flon which is the working medium flowing inthe second evaporator 3B in the second Rankine cycle 2B mounted at thelocation downstream of the exhaust emission control device 8 has a lowboiling point and hence, can be converted into a vapor easily by thelow-temperature exhaust gas immediately after the start of, or duringthe low-load operation of the internal combustion engine 1 to operatethe expander 4 without hindrance.

[0082] After completion of the warming operation of the internalcombustion engine 1, or during the high-load operation of the internalcombustion engine 1, the catalyst in the exhaust emission control device8 is sufficiently raise in temperature and activated, and thetemperature of the catalyst detected by the temperature sensor 9 exceedsthe preset temperature and hence, the first supply pump 6A in the firstRankine cycle 2A is driven by the command from the electronic controlunit 10. Thus, the water is supplied to the first evaporator 3A in thefirst Rankine cycle 2A mounted at the location upstream of the exhaustemission control device 8, and the resulting vapor is supplied to thecylinders 33 which are the high-temperature expanding portions of theexpander 4 to drive the rotary shaft 21. At the same time, the penteneor the substitute flon is supplied to the second evaporator 3B in thesecond Rankine cycle 2B mounted at the location downstream of theexhaust emission control device 8, and the resulting vapor is suppliedto the vane chambers 50 which are the low-pressure expanding portions ofthe expander 4, thereby driving the rotary shaft 21. The working mediumflowing through the first evaporator 3A on an upstream side where thetemperature of the exhaust gas is higher at that time, has the higherboiling point, and the second working medium flowing through the secondevaporator 3B on a downstream side where the temperature of the exhaustgas is lower at that time, has the lower boiling point, and hence, theheat energy of the exhaust gas can be recovered further effectively. Theshaft torque generated in each of the cylinders 33 and the shaft torquegenerated each of the vane chamber 50 are united together in theexpander 4 and output to the common rotary shaft 21 and hence, a specialpower-uniting means is not required, leading to a simplified structure.

[0083] Although the embodiment of the present invention has beendescribed in detail, it will be understood that various modifications indesign may be made without departing from the subject matter of thepresent invention.

INDUSTRIAL APPLICABILITY

[0084] As discussed above, the Rankine cycle system for the internalcombustion engine according to the present invention can be suitablyutilized as a power source for traveling of a vehicle, but may beutilized to any other application.

What is claimed is:
 1. A Rankine cycle system for an internal combustion engine, comprising a first Rankine cycle (2A) operated by a first working medium and a second Rankine cycle (2B) operated by a second working medium, each of the Rankine cycles (2A and 2B) being comprised of an evaporator (3A, 3B) for heating a liquid-phase working medium by waste heat from the internal combustion engine (1) to generate a vapor, an expander (4) for converting the heat energy of the vapor discharged by said evaporator (3A, 3B) into a mechanical energy, a condenser (5A, 5B) for cooling the vapor discharged by said expander (4) to return the vapor into the liquid-phase working medium, and a supply pump (6A, 6B) for supplying the water discharged by said condenser (5A, 5B) to said evaporator (3A, 3B), wherein said evaporator (3A) in said first Rankine cycle (2A) and said evaporator (3B) in said second Rankine cycle (2B) are respectively disposed at locations upstream and downstream of an exhaust emission control device (8) mounted in an exhaust passage (7) for the internal combustion engine (1); said first working medium is of a boiling point higher than that of said second working medium; and the capacity of said supply pump (6A) in at least said first Rankine cycle (2A) is variable.
 2. A Rankine cycle system for an internal combustion engine according to claim 1, wherein said expander (4) includes higher-pressure expanding portions (33) and lower-pressure expanding portions (50), so that outputs from both of said expanding portions (33 and 50) can be united together and output from a common rotary shaft (21); the vapor of said first working medium is supplied to said higher-pressure expanding portions (33); and the vapor of said second working medium is supplied to said lower-pressure expanding portions (50). 